I have also had the same problem...I do think it is probably not a big deal, but I'm not sure

In my case, it led me to examine how I might have set the pedal up...and if that was something I could adjust. I thought I wanted a higher footboard than came stock on the 9000 so I raised it..Didn't really do much in terms of improving the feel for what I thought I was wanting...

Also, I had my beater pretty far back...not right or wrong there I guess...but that weight on the end of the beater rod is a torque arm and the weight ion the torque arm will cause more force in pulling the board back in rebound action

So the combination of my spring tension, beater height off the mounting hole, beater position back from the batter head and pedal height looked to be the cause. And I mucked with all of that right after I bought the pedal.

I adjusted those some and was able to cut down and virtually eliminate the rebound chain smack...thats my experience at least and my playing style could be way different than yours so there might not be a correspondence